Method of manufacturing an extruded metal component

ABSTRACT

The manufacture of an extruded metal component of the kind including a hollow substantially cylindrical body defining one or more axially extending splines at its external surface involves engaging a first punch with one end of a hollow, substantially cylindrical metal billet. The first punch is then used to perform an extrusion operation on the billet by causing the billet to undergo movement relative to a die cavity. The extrusion operation is arranged to cause material of the billet to flow so as to produce the required one or more axially extending splines and, during the extrusion operation, a load is applied to a second punch to urge the second punch against te other end of the billet. The load applied to the second punch is such that the second punch is moved relative to the die cavity by the material being extruded, but at the same time the material being extruded is shaped by the second punch so as to substantially fill the die cavity and thereby define the end of the component corresponding to the other end of the billet.

United States Patent [191 Tranter METHOD OF MANUFACTURING AN EXTRUDED METAL CONIPONENT [75] Inventor: David Thomas Tranter, Kenilworth,

England [73] Assignee: The Lucas Electrical Company Limited, Birmingham, England [22] Filed: July 1, 1974 [21] Appl. No.: 484,787

Primary ExaminerLowell A. Larson Assistant ExaminerRobert M. Rogers Attorney, Agent, or Firml-lolman & Stern was [ ABSTRACT The manufacture of an extruded metal component of the kind including a hollow substantially cylindrical body defining one or more axially extending splines at its external surface involves engaging a first punch with one end of a hollow, substantially cylindrical metal billet. The first punch is then used to perform an extrusion operation on the billet by causing the billet to undergo movement relative to a die cavity. The extrusion operation is arranged to cause material of the billet to flow so as to produce the required one or more axially extending splines and, during the extrusion operation, a load is applied to a second punch to urge the second punch against the other end of the billet. The load applied to the second punch is such that the second punch is moved relative to the die cavity by the material being extruded, but at the same time the material being extruded is shaped by the second punch so as to substantially fill the die cavity and thereby define the end of the component corresponding to the other end of the billet.

6 Claims, 1 Drawing Figure METHOD OF MANUFACTURING AN EXTRUDED METAL COMPONENT This invention relates to a method of manufacturing an extruded metal component of the kind including a hollow substantially cylindrical body defining one or more axially extending splines at the external surface of the body.

A method, according to the invention, comprises the steps of:-

a. starting with a hollow, substantially cylindrical metal billet,

b. engaging a first punch with one end of the billet and using said first punch to perform an extrusion operation on the billet by causing the billet to undergo movement relative to a die cavity, the extrusion operation being arranged to cause material of the billet to flow so as to produce the required one or more axially extending splines and thereby form the required component, and

0. during the extrusion operation, urging a second punch against the other end of the billet, the second punch being moved relative to the die cavity by the material which is being extruded and causing said material to substantially fill the die cavity during the extrusion operation and define the end of the component corresponding to said other end of the billet.

Preferably, the load applied to the second punch to urge the second punch against said other end of the billet during the extrusion operation is substantially equal to the product of the yield stress of the billet and the area of said other end of the billet in contact with the second punch.

Preferably, the second punch is shaped complementarily with the end of the component corresponding to said other end of the billet.

Preferably, the second punch is used to eject the component from the die cavity after the extrusion operation.

Preferably, the portions of the walls of the die cavity which produce said axially extending splines are cut back along their axially extending, radially innermost edges and from a position adjacent their ends remote from the second punch.

Conveniently, the first punch carries a projecting mandrel of the shape of the bore in the component.

The accompanying drawing is a part-sectional side i view illustrating a method, according to one example of the invention, of manufacturing an extruded steel component of the kind specified.

Referring to the drawing, in said one example it was required to produce the component shown at 11. The component was intended for use as a pinion for a road vehicle starter motor and included a hollow, substantially cylindrical body 12 of circular cross section. At one end 12a, the body 12 was formed along part of its length with a plurality of equiangularly spaced, axially extending grooves 13 the depth of which tapered to zero at their ends remote from the end 12a. The grooves 13 thus defined a plurality of equiangularly spaced, axially extending splines 14 at the external surface of the body 12, the splines lying on a circle having a diameter slightly smaller than the external diameter of the non-grooves portion 12b of the body 12.

The component 11 was manufactured from a cylindrical, hot rolled, centreless turned steel bar, the steel used in the bar having the following composition by weight: carbon 0.21 percent, manganese 1.24 percent.

silicon 0.3 percent. sulphur 0.033 percent, phosphorus 0.06 percent, nickel 0.13 percent. chromium 0.23 percent. molybdenum 0.15 percent and copper 0.15 percent, the remainder being iron. The steel bar was initially turned toproduce a hollow, substantially cylindrical billet of length 1 inch and external diameter 1.16 inches, the latter value being substantially equal to that required for the external diameter of the portion 12b of the body. The turning operation was also arranged so that the bore in the billet had a diameter of 0.522 inch along most of its length but was relieved at one end thereof, these dimensions and shaping being substantially the same as those required for the bore in the body 12. Moreover, the turned billet was arranged so that at each of its axial ends the external peripheral edge of the billet was curved so as to lie on a circle of 3/32 inch radius.

After the turning operation, theresultant hollow billet was heat treated to re-crystallize the work hardened ferrite grains in the steel. This was conveniently achieved by passing the billet through a conveyor furnace at a speed of 2.5 inches per minute, with the furnace temperature being held at between 710 and 720C and the furnace being supplied with an exothermic gas. After re-crystallisation, the hollow billet was lubricated using standard phosphating and soaping treatment and was then transferred to an extrusion die 15 supported on the base 16 of a press 17.

The die 15 included a cylindrical die cavity 18 of circular cross section and diameter substantially equal to the maximum external diameter of the component 11. At one end 18a, the walls of the die cavity 18 were provided with a plurality of equiangularly spaced projecting portions 19 which extended into the die cavity and defined the shape of the axially extending grooves 13. Thus, the depth of the portions 19 tapered to zero at their ends remote from the end 180. Furthermore the radially innermost edges of the portions 19 were cut back from a position adjacent their tapering ends, as is shown at 21 in the drawing. Thus, along the majority of their lengths, the portions 19 extended radially into the die cavity 18 by a distance slightly less than the depth of the grooves 13 to be produced in the component 11.

Production of the component 11 from the hollow billet was effected by forcing the billet into the die cavity 18 from the other end 18b thereof by means of a first punch 22 which was urged against the end of the billet remote from the relieved portion of the bore therein and which in one practical embodiment applied a load of tons to the billet. As the billet was moved into the die cavity 18, it engaged the tapering ends of the portions 19, whereafter further movement of the punch 22 displaced metal of the billet. The displaced metal flowed towards the end 18a of the die cavity between the portions 19 so as to produce the splines 14 of the required component 11. The provision of the steps 21 in the portions 19 was found to reduce the friction between the displaced metal of the billet and the die cavity, so reducing the load on the punch 22. Moreover, the punch 22 was provided with a projecting mandrel 23 which was received in the bore in the billet during the extrusion operation so as to ensure that extrusion produced the required bore in the component 11.

Slidably received in the die cavity 18 during the extrusion process was a hollow second punch which extended into engagement with the billet from the end 18a of the die cavity. The end of punch 24 in contact with the billet was substantially flat, although the exterior of the punch 24 carried the same spline form as required for the component 11. Further, as the punch 22 was moved into the die cavity 18 to effect extrusion of the billet, the punch 24 was urged against the end of the billet remote from the punch 22. The load applied to the punch 24 was of course arranged to be less than that applied to the punch 32 so that as the extrusion operation progressed the punch 24 was moved by the billet relative to the die cavity 18 and the mandrel 23 was moved into the bore in the punch 24. However, the load applied to the punch 24 was arranged to be sufficient to cause the material of the billet which was flowing towards the end 18a of the die cavity to substantially fill the cavity during the extrusion operation and, define the end 12a of the component. In this way it was found that the extrusion process produced splines 14 which accurately conformed to the shape of the die cavity 18 along the complete length of the splines. Also, it was found that by following the above procedure the extruded material substantially retained the shape of the billet rather than being shaped by the punch 24 so that the external peripheral edge of the splined end 12a of the resultant component had the same curvature as the corresponding edge of the billet. In this respect, it is to be understood that this curvature was necessary for the component to be used as the pinion ofa road vehicle starter motor and would otherwise have had to have been applied to the component in a separate operation. Moreover, the relieved portion of the bore in the billet was substantially retained in the bore of the extruded component, this form also being required for use of the component as a starter motor pinion.

Using the extrusion process described, it was found to be possible to ensure that the required shaping was obtained for the end 12a of the component by arranging that the load applied to the punch 24 was substantially equal to the product ofthe yield stress of the billet and the area of the billet in contact with the punch 24. In practice the precise loading for the punch 24 was obtained by performing a trial extrusion on a billet with the punch load being set at a value exactly equal to said product of yield stress and area. The resultant component was then observed and if the spline form was not fully completed, the load on the punch 24 was increased by percent whereas if material ofthe billet had been forced between the punch 24 and the projecting portions 19 the punch load was decreased by 5 percent. Subsequent extrusion operations were than found to produce components 12 in which the required shaping was accurately reproduced. In said one practical embodiment, the material billet had a yield stress of t.s.i. and, allowing for the shaping of the punch 24 and the bore in the billet, the area of the billet in contact with the punch 24 was 0.35in A trial extrusion operation was therefore performed with the loading of the punch 24 set at 10.5 tons and it was found that some material was extruded between the punch 24 and the projecting portions 19. The punch load was therefore decreased to 10 tons and subsequent extrusion operations produced components 12 of the required shape.

Following extrusion, the punch 22 was removed from the die cavity 18 and the punch 24 was moved towards the end 18b of the die cavity so as to eject the finished component from the die.

It is to be appreciated that the billet used to produce the component 11 could have been produced by a cropping and dumping sequence, instead of by the turning operation employed in the above example.

I claim:

1. A method of manufacturing an extruded metal component of the kind including a hollow substantially cylindrical body defining one or more axially extending splines at the external surface of the body, the method comprising the steps of:

a. starting with a hollow, substantially cylindrical metal billet,

b. engaging a first punch with one end of the billet and using said first punch to perform an extrusion operation on the billet by causing the billet to undergo movement relative to a die cavity, the extrusion operation being arranged to cause material of the billet to flow so as to produce said one or more axially extending splines, and

c. during the extrusion operation, applying a load to a second punch so as to urge said said second punch against the other end of the billet, said load being such that the second punch is moved relative to the die cavity by the material which is being extruded but said material being extruded is shaped by said second punch so as to substantially fill the die cavity during the extrusion operation and thereby define the end of the component corresponding to said other end of the billet.

2. A method as claimed in claim 1 wherein the load applied to the second punch to urge the second punch against said other end of the billet during the extrusion operation is substantially equal to the product of the yield stress of the billet and the area of said other end of the billet in contact with the second punch.

3. A method as claimed in claim 1 wherein the second punch is shaped complementarily with the end of the component corresponding to said other end of the billet.

4. A method as claimed in claim 1 wherein the second punch is used to eject the component from the die cavity after the extrusion operation.

5. A method as claimed in claim 1 wherein the portions of the walls of the die cavity which produce said axially extending splines are cut back along their axially extending, radially innermost edges and from a position adjacent their ends remote from the second punch.

6. A method as claimed in claim 1 wherein the first punch carries a projecting mandrel of the shape of the bore in the component.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION PATENT NO. 3,911,715 Q DATED October 14, 1975 INVENTOWS) 1 David Thomas Tranter It is certified that error appears in the above-identified patent and that said Letters Patent are hereby corrected as shown below:

[30] Foreign Priority Data:

Great Britain No. 32446/73 filed July 6, 1973 Signed and Scaled this Sixth Day of January1976 0 [SEAL] Arrest:

RUTH c. MASON c. MARSHALL DANN Attesling Officer (ummissimwr 0f Patents and Trademarks O 

1. A method of manufacturing an extruded metal component of the kind including a hollow substantially cylindrical body defining one or more axially extending splines at the external surface of the body, the method comprising the steps of: a. starting with a hollow, substantially cylindrical metal billet, b. engaging a first punch with one end of the billet and using said first punch to perform an extrusion operation on the billet by causing the billet to undergo movement relative to a die cavity, the extrusion operation being arranged to cause material of the billet to flow so as to produce said one or more axially extending splines, and c. during the extrusion operation, applying a load to a second punch so as to urge said said second punch against the other end of the billet, said load being such that the second punch is moved relative to the die cavity by the material which is being extruded but said material being extruded is shaped by said second punch so as to substantially fill the die cavity during the extrusion operation and thereby define the end of the component corresponding to said other end of the billet.
 2. A method as claimed in claim 1 wherein the load applied to the second punch to urge the second punch against said other end of the billet during the extrusion operation is substantially equal to the product of the yield stress of the billet and the area of said other end of the billet in contact with the second punch.
 3. A method as claimed in claim 1 wherein the second punch is shaped complementarily with the end of the component corresponding to said other end of the billet.
 4. A method as claimed in claim 1 wherein the second punch is used to eject the component from the die cavity after the extrusion operation.
 5. A method as claimed in claim 1 wherein the portions of the walls of the die cavity which produce said axially extending splines are cut back along their axially extending, radially innermost edges and from a position adjacent their ends remote from the second punch.
 6. A method as claimed in claim 1 wherein the first punch carries a projecting mandrel of the shape of the bore in the component. 